1. Field of the Invention
The present invention relates to a power plant which includes an internal combustion engine with a variable compression ratio system which involves changing the position of the axis of rotation of a crankshaft, and which includes a transmission to which power of the crankshaft of the internal combustion engine is transmitted.
2. Background
A known internal combustion engine has a variable compression ratio system achieved by changing the position of the axis of rotation of a crankshaft in order to change a compression ratio. Such a system is disclosed in, for example, Japanese Patent Application Laid-open No. Sho 58(1983)-57040. In the internal combustion engine thereof, a crankshaft is rotatably supported on a cylinder block through an eccentric bearing. The eccentric bearing is activated into a rotational motion by a drive unit. As a result, the position of the axis of rotation is changed and the position of the top dead center is changed, hence changing the compression ratio.
In the meantime, in a power plant which includes a transmission with an input shaft whose axis of rotation is on a parallel with the axis of rotation of a crankshaft, when the position of the axis of rotation of the crankshaft is changed to change the compression ratio as in the above-described conventional technology, the shaft distance between the crankshaft and the input shaft is changed. As a result, it is difficult to make appropriate power transmission from the crankshaft to the input shaft. In addition, when power of the crankshaft is transmitted through a transmission which is formed by a gearing system, the shaft distance is changed so that the backlash between gears being engaged with each other is changed, causing gear noise to increase.